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For Cities With Water Shortages, Don't Blame It On The Rain

Though many places around the country barely have enough to drink, they’re ignoring a massive free source of water: the stuff up in the clouds, which could fulfill almost all of our water needs if we just used it right.

Water is an increasingly scarce resource. And not just in developing countries. According to the Environmental Protection Agency, at least 36 states will face water shortages by 2013.

At the same time, most of the water that falls out of the sky for free—rain, that is—just flows straight into the gutter. Why don’t we make better use of it?

Why, indeed. Researchers from the Natural Resources Defense Council (NRDC) recently profiled eight American cities and found that, depending on the city, rainwater collection systems on just half of the available rooftop space could supply between 21% and 75% of annual water needs (PDF). They would also save residents a combined $90 billion in municipal water fees. (As a bonus, rainwater collection also reduces the amount of polluted runoff that flows into lakes, rivers, and oceans.)

The NRDC based its model for each city on several factors including available roof area, annual rainfall, and local water rates. The $90 million figure assumes these eight cities have rainwater collection systems on half of their roof area, not all rainwater is captured because some storms dump more than the collection systems can handle, and captured rainwater isn’t all used immediately.

This model also assumes that rainwater captured at residences is only used for outdoor, non-potable purposes, like washing a car or watering plants. This kind of outdoor water use can constitute 30% to almost 60% of overall domestic demand. In theory, however, captured rainwater could also be used indoors—to flush toilets, for example.

Capturing rainwater seems like a no-brainer, right? The problem is that regulations governing how water can be captured and used are incredibly inconsistent across the country. Tucson, Arizona requires commercial developments to have rainwater collection systems. In Colorado, it’s illegal. In many cities, residential rainwater collection is legal, but the water can only be deployed for outdoor uses.

So that’s one problem. It’s a regulatory mess. Another problem is that municipal water is underpriced almost everywhere, making one key incentive to capture rainwater—money—a little less keenly appreciated.

If you want to capture rainwater yourself, there are lots of good products on the market, from this giant "pillow" to this elegant little downspout accessory. Check your local laws.